Centralization of documentation should definitely solve a lot of problem. About User documentation I do agree that every app are different but core KDE development tools or any kind of development documentation/tutorial should be centralized. But even in case of User documentation there should be proper guidelines and APIs to organize all the documentation from KDE applications.

While develop.kde.org website exists. It is kind of unmaintained I think. There are a lot of bug reports in it's gitlab repo but most of them are completely unanswered and also there are tons of broken links in the page from what I have seen. Aside from that build instruction of 99% of KDE apps is lacking. It is really difficult to even find a right way to setup development on your machine.